[RHEV] rhevm upgrade from 3.0 to 3.1 failed with "Skipping yum rollback" error message.

Issue

• While trying to upgrade the rhevm from 3.0 to 3.1, upgrade failed due to the lower version of virtio-win package and failed to roll back to rhevm 3.0 with the following error messages and presently no rhevm packages are available in the system:

2013-07-30 16:25:54::DEBUG::common_utils::378::root:: stderr = Error: Package: rhevm-3.1.0-55.el6ev.noarch (rhel-x86_64-server-6-rhevm-3.1)
           Requires: virtio-win >= 1.6.3-3
           Installed: virtio-win-1.4.0-1.el6.noarch (@rhel-x86_64-server-supplementary-6)
               virtio-win = 1.4.0-1.el6

2013-07-30 16:25:54::DEBUG::common_utils::379::root:: retcode = 0
2013-07-30 16:25:54::DEBUG::rhevm-upgrade::596::root:: DB Restore completed successfully
2013-07-30 16:25:54::DEBUG::rhevm-upgrade::1463::root:: Skipping yum rollback
2013-07-30 16:25:54::DEBUG::rhevm-upgrade::659::root:: starting ovirt-engine service.
2013-07-30 16:25:54::DEBUG::common_utils::339::root:: Executing command --> '/sbin/service ovirt-engine start'
2013-07-30 16:25:54::DEBUG::common_utils::377::root:: output =
2013-07-30 16:25:54::DEBUG::common_utils::378::root:: stderr = ovirt-engine: unrecognized service

2013-07-30 16:25:54::DEBUG::common_utils::379::root:: retcode = 1
2013-07-30 16:25:54::ERROR::rhevm-upgrade::1521::root:: Traceback (most recent call last):
  File "/usr/bin/rhevm-upgrade", line 1514, in <module>
  File "/usr/bin/rhevm-upgrade", line 1467, in main
  File "/usr/bin/rhevm-upgrade", line 692, in runFunc
  File "/usr/bin/rhevm-upgrade", line 663, in startEngine
  File "/usr/share/ovirt-engine/scripts/common_utils.py", line 382, in execCmd
  Exception: Error: Can't start ovirt-engine